This invention relates generally to injection molding and more particularly to an injection molding system in which a circumferential locating flange extends from a heated nozzle or manifold outwardly across an air space to locate the nozzle in a well in a cooled cavity plate in which it is received.
Many injection molding systems are known which have a heated nozzle extending from a heated manifold into a well in a cooled cavity plate to convey pressurized melt through a melt passage to a gate leading to a cavity. In order to minimize heat loss from the heated nozzle to the cooled cavity plate, an insulative air space is provided between them. However, the air space must be bridged by means which accurately locates the nozzle in the well in the cavity plate and also takes the machine nozzle pressure. Usually in order to maintain accurate alignment of the nozzle in the well, sealing and locating means are provided near the front end of the nozzle and locating means are provided towards the rear end of the nozzle. For example, the applicant's U.S. Pat. No. 4,579,520 which issued Apr. 1, 1986 shows a heated nozzle seated on an insulation bushing with a nose portion extending into an opening in the cavity plate leading to the cavity. The applicant's U.S. Pat. No. 4,768,283 which issued Sept. 6, 1988 and U.S. Pat. No. 4,771,534 which issued Sept. 20, 1988, as well as U.S. Pat. No. 4,588,367 to Schad which issued May 13, 1986 disclose nozzles having insulating flanges which extend across the insulative air space into contact with the surrounding cavity plate.
Other nozzles having insulating rings or hoops with circumferentially extending groves or ridges are disclosed in the applicant's U.S. Pat. No. 4,777,348 which issued Oct. 11, 1988 and Canadian application Ser. No. 569,756 filed June 17, 1988. Another arrangement to provide additional insulation for a heated nozzle is shown in the applicant's U.S. Pat. No. 4,795,338 which issued Jan. 3, 1989. U.S. Pat. No. 4,705,473 to Schmidt which issued Nov. 10, 1987 shows a valve pin bushing having a locating flange mounted between each nozzle and the manifold. Thus, nozzles having locating flanges are known and are satisfactory for many applications. However, in systems for molding materials having a critical temperature window, heat loss from the heated nozzle and manifold to the cooled cavity plate through the locating flange has become increasingly critical to successful operation of the system.